Electroluminescent photocopying



March 8, 1966 J. w. MAUCHLY 3,238,859

ELECTROLUMINESGENT PHOTOCOPYING Filed July 5, 1962 2 Sheets-SheetlVAR/ABLE A. 6'. SOURCE 62 v INVENTOR 60 JOHN m MAUCHU QJPMAZSW ATTORNEYMarch 8, 1966 J. w. MAUCHLY 3,238,859

ELECTROLUMINESCENT PHOTOCQPYING Filed July 5, 1962 2 Sheets-Sheet 2INVENTOR.

JOHN W MAUCHLV AMM SW ATTORNEY United States Patent 3 238,859ELECTROLUMINESCENT PHOTOCOPYING John W. Mauchly, Ambler, Pa., assignorto Mauchly Associates, Inc., Fort Washington, Pa., a corporation ofPennsylvania Filed July 3, 1962, Ser. No. 207,214 2 Claims. (Cl. 95-73)In general, this invention relates to a new and different method ofphotocopying letters, drawings, printed matter or other .materal. Moreparticularly, it relates to the use of an electroluminescent sheet as alight source for photocopying.

Heretofore, many methods have been devised for making copies of printedmatter, drawings, or the like on loose sheets. Some methods call forpressing sheets flat under a glass plate while exposing a photosensitivepaper in contact with the material to be copied. Another method would beto place the copy material and the photosensitive paper through rollersfollowing a curved path around a light source. However, these methodsare either clumsy and awkward or completely impractical when applied tothe copying of pages in a bound book. Even when used for such purpose,it is necessary by reason of the process utilized to bend the binding ofthe book and thereby injure it. Additionally, it is diificult to photocopy quickly more than one page of the bound book.

In the prior photocopying methods, if it is desired to change for anyreason the type of photosensitive paper, i.e. from paper sensitive toone color of light rather than another, it was necessary to place alight filter in front of the light source. This too called for bulkyequipment and the necessity of keeping a variety of light filtersavailable.

The present photocopying devices commercially available are extremelybulky and require a permanent installation. Thus, they could not beeasily transported by one who had photocopying needs in various places.

It is the general object of this invention to avoid and overcome theforegoing and other diificulties of the prior art by the provision of anew and better photocopying system.

Another object of this invention is to provide a better photocopyingsystem which utilizes a flexible electroluminescent sheet as the lightsource.

Another object of this invention is to provide a better reflex copyingsystem which can be utilized to photocopy a plurality of pages in a bookin one operation.

Another object of this invention is to provide a new and betterphotocopying device which is lightweight and easy to transport.

Another object of this invention is to provide a simple and betterphotocopying system in which the light source is variable both in colorand in magnitude.

Another object of this invention is to provide a new method ofphotocopying two adjacent pages in a book in a single operation from asingle source of light.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in thedrawings forms which are presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is a pictorial view of a flexible laminated electroluminescentlamp utilized in the present invention, the various constitutent layersbeing delaminated or peeled open at one corner to show the internalconstruction.

FIGURE 2 is a pictorial view illustrating the first step in photocopyingtwo adjacent pages in a book in accordance with the present invention.

FIGURE 3 is a partial cross section view of the apparatus of FIGURE 2 inthe photocopying stage.

may be any flexible electroluminescent light source.

3,238,859 Patented Mar. 8, 1966 FIGURE 4 is a second embodiment of thepresent invention utilizing a plurality of electroluminescent sheets tophotocopy a group of pages in a book simultaneously.

FIGURE 5 is a pictorial view illustrating the first step in copying twopapers utilizing apparatus built in accordance with the principles ofthe present invention.

Referring to the drawings, and more particularly to FIGURE 1, there isshown a flat rectangular electroluminescent sheet 10. This sheet is madeup of flexible components laminated together and is entirely sealed inplastic material. The sheet is energized by applying an alternatingvoltage to the copper screen terminals 12 and 14 projecting laterallyfrom the edge of the plastic envelope.

The electroluminescent sheet 10 shown in FIGURE 1 In the interest ofclarity, one sample electroluminescent sheet which might be utilized inthe present invention is shown in detail.

The lowermost film and the uppermost film 16 which form respectively theunderside and topside of the envelope in the finished lamp consist ofsheets of thermoplas- -tic material which fiows under heat and pressureand welds together along the margins. The material selected must bereasonably tough and stable, in addition to being light-transmitting andpreferably flexible. Examples of such materials are polyethylene,polytetrafluoroethylene, polystyrene, and fluoride polymers.

A rectangular sheet 28 of low-density polyethylene sheet is placed undera rectangular sheet of conducting micro-fiber glass paper 26 coated withan insulating layer 24 of high dielectric constant material andthereover a light producing layer 22 of electroluminescent phosphor isplaced over the lowermost polyethylene sheet 30 leaving a clear marginall-around. A second sheet of conducting micro-fiber glass paper 20 islaid over the coated sheet 26 leaving a narrow margin of coated sheetuncovered all-around. Preferably a thin sheet 18 of low-densitypolyethylene is placed over the conducting glass paper and convenientlyis of the same size as the high-density envelope sheets 16 and 30, andextends to their margins. The first sheet of low-density polyethylene 28is also of the same size. During the laminating process, the low densitypolyethylene sheets 18 and 28 are substantially liquified and forcedthrough the porous glass paper 20 and 26. Thus the glass paper sheets 26and 26 are bound in place being partly embedded in low-densitypolyethylene sheets and also cemented to the phosphor layer 22. Thejuxtaposed margins of the thermoplastic sheets 16, 18, 28 and 30 projectbeyond the edges of the glass paper sheets and are fused or sealedtogether. The high dielectric constant material coating 24 may be a thininsulating layer of barium titanate dispersed in an organic polymericmatrix. The electroluminescent layer can consist of phosphor such aszinc sulfide-zinc oxide with suitable activators such as copper,manganese, lead or silver likewise dispersed in an organic polymericmatrix. Examples of organic polymeric matrices are cellulose nitrate,polyvinyl chloride, cellulose acetate, andepoxy cements.

The conducting glass paper sheets 20 and 26 consist of commerciallyavailable micro-fiber glass paper which is made conducting by dipping ina solution of a metal salt which upon drying and baking at an elevatedtemperature forms a con-ducting coating. It should be appreciated thatwhen the flat flexible sheet 10 is completed, it is less than .05 inchthick.

In order to energize the electroluminescent sheet, it is necessary toapply an alternating voltage between the conductive layers, that is, tothe micro-fiber glass paper sheets 20 and 26. This may conveniently beeffected by means (J of flattened flexible copper braids or ribbons 32and 34, the former being laid over the conductive glass paper 20, thatis, between the glass paper and low-density polyethylene sheet 18, andthe latter being laid under the micro-fiber glass paper sheet 26 betweenthe glass paper and the low-density polyethylene sheet 28. The copperribbons 32 and 34 extends substantially to the edge of the polyethyleneenvelope sheets 16 and 30 at one end and there overlie respectively apair of laterally projecting copper screens 12 and 14. During thelaminating step, the copper ribbons become embedded in the thermoplasticsheets and are at the same time pressed against the glass paper sheets.The ends of the copper ribbons and the copper screens 12 and 14 likewisebecome embedded in the thermoplastic envelope sheets and are pressed inmutual contact. The ends of the screens projecting beyond thethermoplastic envelope serve as contact terminals. It will beappreciated that when the electroluminescent lamp is lit, the phosphoris energized and lights up to the margin of the conductive glass paper.The band between the margin of the conductive glass paper and the edgeof the sheet is not illuminated but is transparent, or at leasttranslucent.

The excitation of the phosphor layer is governed by the strength of theelectric field requiring constant thickness in the various layers of thefinished electroluminescent lamp. It is to be appreciated that theconducting glass paper may be replaced by a light-transmitting flexiblesheet of high-melting point plastic such as Mylar coated with a thinlayer of evaporated metal or a semi-conductor such as gold metal orcuprous iodide.

In FIGURE 2, there is shown one preferred embodiment of the presentinvention. When it is desired to photocopy two adjacent pages 40 and 42in a book 44, it is only necessary to do the following. The book 44 isOpened to the pages, and therein inserted first a photosensitive sheet38, the electroluminescent sheet 10 and a photosensitive sheet 36 inplace on one page 42. The book 44 is then closed and acts as a pressholding the three sheets 36, 10 and 38 flat against the pages 40 and 42to be copied.

The flexible electroluminescent sheet 10 has its terminals 12 and 14connected to a variable alternating current source 46. The alternatingcurrent source 46may be one such as shown in US. Patent 2,937,298. Thealternating current source 46 is capable of varying'its voltage andfrequency output.

The color and intensity of light emitted by the electroluminescent sheetdepend not only on what phosphors are used in the manufacture of thesheet, but also on the frequency of the electrical voltage used toexcite it. As the frequency of the alternating current source goes up,the color of the emitted light from the electroluminsecent sheet shiftstowards the colors having shorter wave lengths.

The intensity of the light is somewhat proportional to the magnitude ofthe applied voltage.

It should be noted, however, that there are other ways of producing allvariations of the spectrum using an electroluminescent sheet. One suchmethod is shown in US. Patent 2,925,532. It should be noted that becauseof the ability to shift the intensity and the color of the lightproduced by the electroluminescent sheet by simple variation of the AC.source, it is possible to tailor the light produced to the particularsensitivity of the photocopying paper used. In this manner, theelectroluminescent sheet has eliminated the need for special filterswhen a change is made in the type of photocopy paper.

In FIGURE 3, there is shown a cross sectional area of the sheets 36 and38 described with reference to FIG- URE 2 in place when the book 44 hasbeen closed. Only pages 40 and 42 of the book 44 have been shown forpurposes of clarity.

Although the present invention is especially useful in reflex copying,it may also be utilized in contact copying if so desired. Additionally,the process shown in FIG- URE 2 is utilized for copying two adjacentpages of a book. It can easily be seen that if only one page of the bookis tobe copied, only one sheet of photosensitive paper is needed.

In FIGURE 2, the electroluminescent sheet 10 is shown sandwiched betweentwo photocopy sheets 36 and 38. Pages 40 and 42 are placed flat againstsheets 36 and 38 respectively.

As shown in FIGURE 3, the face of the page 42 to be copied is placed incontact with the support 48 of photocopying sheet 38 which has on itsother face a lightsensitive emulsion layer 50. The support 48 has arelatively high transparency; it may consist of a suitable paper, and itcontains a non-volatile agent having such characteristics as areindicated below. When the photocopying paper 38 is exposed to light, theemulsion coated surface 50 is directed towards the light source. Theincident light which successively passes through the emulsion layer 50and the support 48 reaches the face to be copied of page 42 and isreflected thereby in proportion of the densities printed on the face ofthe page.

It should be noted that for purposes of example, the light-sensitiveelement 38 has been shown with it's emul sion coated surface directedtoward the light source. However, it is within the scope of thisinvention to have a reflex copy process where the emulsion coatedsurface is in contact with the document to be copied. The arrangementshown in FIGURE 2, wherein the support of the light-sensitive elementrather than the emulsion is in contact with the page, makes it possibleto obtain directly a non-laterally inverted copy.

The light-senstive element, or photocopy paper 36, also consists of asupport 54 and an emulsion layer 52. The emulsion layer 52 is directedtoward the light source 10 while the support 54 is adjacent the page 40to be copied. The light-sensitive emulsion layers 52 and 50 are prefer-.ably made of a usual lgelatino-silver halide emulsion. may be anemulsion of the type giving a negative copy from a positive original.Preferably, a reversal emulsion is used, especially a direct positiveemulsion which upon development in a usual black and white developer,directly gives a positive image from a positive original. Thus, usingthe type of photocopy paper 36 and 38 discussed above, it is possible bymeans of a single exposure followed by a single development step toobtain a nonlaterally-inverted positive copy of any original.

The book 44 acts as an opaque support so that the printed matter on theback of pages 40 and 42 does not interfere with the copying of thematerial on the sides adjacent photocopying paper 36 and 38. The bookalso acts as a press to hold the photocopy paper 36 and 38 and theelectroluminescent sheet 10 between the pages 40 and 42 without anyundue strain on the binding of the book.

After exposing the photocopy paper 36 and 38 by exciting theelectroluminescent sheet 10 from the alternating current source 46 for agiven period of time, the photocopy paper is subjected to the usualphotographic processing order to develop the latent image. Thistreatment usually comprises a development step and a subsequent fixingor stabilizing step and, if desired, a washing step. On the other hand,it may be desirable to use rapid processing where required which wouldonly call for a single development and a subsequent stabilizationwithout any washing step.

The supports 54 and 48 are transparentized paper, made such byincorporating a non-volatile transparentizing agent and selecting suchtransparentizing agent so that it can be eliminated from the supportwhile the exposed element is being processed in one of the photographicbaths. By non-volatile, it is meant that the transparentizing agent isnot eliminated during storing, whatever the hygrometric conditions maybe. One such transparentizing agent is sodium lactate. After exposure,the

transparentizing agent is normally completely eliminated in thedevelopment process.

It can be seen that if only one photocopy is desired with a singleelectroluminescent sheet, it is possible to substitute for one of theconducting layers in the electroluminescent sheet a light-reflectiveconducting layer so as to direct all light produced by the sheet towardthe photocopy paper. However, when the present invention is utilized inphotocopying pages of a book, the book itself acts as a light-reflectivebacking so as to direct all of the light toward the light-sensitivepaper and the page to be copied.

In FIGURE 4, there is shown a second embodiment of the presentinventionutilizing a plurality of electroluminescent sheets and photocopy'paperto simultaneously photocopy a portion of a book. Normally, when itbecame necessary to photocopy pages of a book by standard photocopyingprocesses, it was necessary to individually copy each page in the book.However, by utilizing the present invention, all the pages which are tobe copied can be duplicated at one time. As shown in FIGURE 4, all thatis necessary is to provide a plurality of electroluminescent sheetsconnected in parallel with the variable A.C. source. Theelectroluminescent sheets have been generally designated as 56, 58, 60and 62. The book 44 is opened to the appropriate pages, photocopy paperis inserted where needed, the electroluminescent sheets are put inplace, and the book closed. The book will act as a press, and oneapplication of electrical energy from the source 46 will expose tall thephotocopy sheets in the book 44.

The present state of the electroluminescent phosphor art requires theuse of a separate alternating current supply capable of high frequenciesand high voltages. This is so as it is the only method of obtainingadequate light intensity from the phosphors so that photocopying may beaccomplished. The norm-a1 house current 120 volts and 60 cycle AC. issuflicient only t produce a small amount of light in the knownelectroluminescent sheets. However, simple, light and easilytransportable converters may be utilized to increase the voltage andfrequency of ordinary house current so that it may be more effectivelyused in the present invention. By so providing a small alternatingcurrent converter, the entire photocopying unit may be stored in assmall a place as a persons briefcase. The electroluminescent sheets donot take up much space. The only limitation in ease of transportationwould be the amount of photocopy paper which could be carried.

In FIGURE 5, there is shown permanent apparatus for photocopying papersutilizing the principles of the present invention. The photocopyingmachine in FIGURE 5 is generally designated by the numeral 64 andconsists of a base or housing 66 and a movable opaque plate 68. Thehousing 66 has at the bottom thereof a tray 70 in which the developingprocess can be completed. A valve 71 at the bottom of the housing 66 isused to drain the developing solution from the tray 70 after it has lostits strength. The opaque plate 68 is used as a press for thephotocopying process and is secured to the housing 66 through uprightvertically slotted hinges 72 and 74 secured to opposite sides of one endof the housing 66. The top face 76 forms the bottom of the press for thephotocopying operation. The top face 76 has a slot 78 therein at the endopposite from the hinges 72 and 74 which cooperates with a lockingmechanism 80 on the plate 68. A handle 82 is operative to disengage thehook or latch 80 from the hole 78 when the plate 68 is to be raised.

An electroluminescent sheet such as the sheet shown in FIGURE 1 could beutilized with the apparatus 64 to photocopy the material shown in FIGURE5. However, in order to obtain more light from a singleelectroluminescent sheet, the double layer electroluminescent sheet 84shown in FIGURE 5 was utilized.

The sheet 84 consists of two back-to-back electroluminescent layers 86and 88 having a common electrically conductive sheet at their matingfaces. This electrically conductive sheet (not shown) is connected to aterminal 92. The outer faces of electroluminescent layers 86 and 88 areconnected to terminals 90 and 94 respectively. The outer faces ofelectroluminescent layers 86 and 88 are transparent and could be made ofa glass fiber fabric such as was discussed with reference to FIGURE 1.The mating faces of the electrically conductive sheet may be transparentalso or, in the alternative, could be manufactured of a light reflectiveelectrically conductive material such as a thin metal foil. By using athin metal foil, the two electroluminescent layers effectively act asseparate electroluminescent lamps whose light transmission isindependent one from another.

A photosensitive matrix 96 is then placed over the electroluminescentlayer 86 with its photosensitive coating on the side opposite from thelayer 86. The photosensitive matrix 96 has a translucent support throughwhich the light emanating from the layer 86 is transmitted to thephotosensitive coating on the matrix 96. A paper 98 which is to becopied is placed face downwardly upon the matrix 96 with thephotosensitive coating adjacent the object 98 to be copied. A similarmatrix 100 is placed under layer 88 with its photosensitive surfacecontiguous with a paper 102 to be copied. The paper 102 is under thematrix 100.

The electroluminescent lamp 84, photocopy matrix paper 96 and 100, andpapers 98 and 102 are then placed between plate 68 and top face 76 inthe manner suggested by the pictorial view in FIGURE 5. The plate 68 isheavy and, therefore, when it is latched by means of hook 80 and hole78, it presses the papers, matrix paper and lamp together. Both the topface 76 and 68 are opaque surfaces. Terminals 90, 92 and 94 areenergized from a suitable source of variable AC. voltage (not shown) toexcite the matrix paper 96 and 100 and produce a negative image thereon.The matrix paper 96 and 100 is then placed in the developing and fixingbath in tray 70 along with positive copy paper to produce a positiveimage of the objects to be copied.

If it is desired to use only coherent light, a polarizing filter couldbe placed over the transparent faces of electroluminescent layers 86 and88.

It can also be seen that if more than one electroluminescent lamp 84 isavailable, more than two papers can be copied. That is, the plate 86 canbe raised so as to accommodate more electroluminescent lamps,photocopying matrix paper, and pages to be copied.

The present invention may be embodied in other specific forms Withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

I claim:

1. Photocopying apparatus comprising a fiat electroluminescent sheet,converter means adapted to be connected to a source of electrical energyand to convert the electrical energy to excite said electroluminescentsheet, connector means for connecting said electroluminescent sheet tosaid converter, said electroluminescent sheet being adapted to bejuxtaposed to a light-sensitive sheet contiguous with an object to becopied to expose said light sensitive sheet and thereby the object, saidconverter including output signal frequency varying means operative tovary said converter output signal frequency in accordance with a desiredcolor of light to be produced by the electroluminescent sheet, the colorof light produced being dependent upon the light sensitivity of thelight-sensitive sheet.

2. Photocopying apparatus comprising a bottom support having a flatrigid opaque surface, a flat rigid opaque press member biased towardcontiguous abutment with said surface, an electroluminescent sheet,connecting means for connecting said electroluminescent sheet to asource of alternating current for exciting said electroluminescentsheet, said electroluminescent sheet being adapted to be juxtaposed tosaid light-sensitive sheet contiguous with an object to be copiedbetween said press member and said surface to said light-sensitive sheetand thereby copy the object, said electroluminescent sheet consisting oftwo separately excited electroluminescent layers having a reflectivecoating therebetween, each of the electroluminescent layers beingadapted to be juxtaposed to a light-sensitive sheet contiguous with anobject to be copied and placed between said press member and saidsurface to expose said light-sensitive sheets and thereby copy theobjects.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS6/ 1954 Australia.

1930 Great Britain. 1/ 1962 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

1. PHOTOCOPYING APPARATUS COMPRISING A FLAT ELECTROLUMINESCENT SHEET,CONVERTER MEANS ADAPTED TO BE CONNECTED TO A SOURCE OF ELECTRICAL ENERGYAND TO CONVERT THE ELECTRICAL ENERGY TO EXCITE SAID ELECTROLUMINESCENTSHEET, CONNECTOR MEANS FOR CONNECTING SAID ELECTROLUMINESCENT SHEET TOSAID CONVERTER, SAID ELECTROLUMINESCENT SHEET BEING ADAPTED TO BEJUXTAPOSED TO A LIGHT-SENSITIVE SHEET CONTIGUOUS WITH AN OBJECT TO BECOPIED TO EXPOSE SAID LIGHT SENSITIVE SHEET AND THEREBY THE OBJECT, SAIDCONVERTER INCLUDING OUTPUT SIGNAL FREQUENCY VARYING MEANS OPERATIVE STOVARY SAID CONVERTER OUTPUT SIGNAL FREQUENCY IN ACCORDANCE WITH A DESIREDCOLOR OF LIGHT TO BE PRODUCED BY THE ELECTROLUMINESCENT SHEET, THE COLOROF LIGHT PRODUCED BEING DEPENDENT UPON THE LIGHT SENSITIVITY OF THELIGHT-SENSITIVE SHEET.
 2. PHOTOCOPYING APPARATUS COMPRISING A BOTTOMSUPPORT HAVING A FLAT RIGID OPAQUE SURFACE, A FLAT RIGID OPAQUE PRESSMEMBER BIASED TOWARD CONTIGUOUS ABUTMENT WITH SAID SURFACE, ANELECTROLUMIESCENT SHEET, CONNECTING MEANS FOR CONNECTING SAIDELECTROLUMIESCENT SHEET TO A SOURCE OF ALTERNATING CURRENT FOR EXCITINGSAID ELECTROLUMINESCENT SHEET, SAID ELECTROLUMINESCENT SHEET BEINGADAPTED TO BE JUXTAPOSED TO SAID LIGHT-SENSITIVE SHEET CONTIGUOUS WITHAN OBJECT TO BE COPIED BETWEEN SAID PRESS MEMBER AND SAID SURFACE TOSAID LIGHT-SENSITIVE SHEET AND THEREBY COPY THE OBJECT, SAIDELECTROLUMINESCENT SHEET CONSISTING OF TWO SEPARATELY EXCITEDELECTROLUMINESCENT LAYERS HAVING A REFLECTIVE COATING THEREBETWEEN, EACHOF THE ELECTROLUMINESCENT LAYERS BEING ADAPTED TO BE JUXTAPOSED TO ALIGHT-SENSITIVE SHEET CONTIGUOUS WITH AN OBJECT TO BE COPIED AND PLACEDBETWEEN SAID PRESS MEMBER AND SAID SURFACE TO EXPOSE SAIDLIGHT-SENSITIVE SHEETS AND THEREBY COPY THE OBJECTS.